Purification of water, such as thermal desalination of salt water using multi-stage flash (MSF) or multiple effect distillation (MED), is a process that receives heat from a low pressure, high quality steam energy source. In this process, low pressure steam is generated with common boiler technology (see, for example, U.S. Pat. Nos. 4,338,199 and 5,441,548).
It is known to use other forms of energy for desalination. For example, U.S. Pat. No. 5,421,962 utilizes solar energy for desalination processes, U.S. 2011/0162952 utilizes energy from a gasification process, and U.S. 2011/0147195 uses waste heat from a power generation plant for the desalination process.
Industry desires to utilize waste heat from catalytic steam-hydrocarbon reforming processes. Catalytic steam-hydrocarbon reforming processes release a large amount of waste heat under various circumstances. One circumstance is when the energy cost is low and less capital is spent on heat recovery. Another circumstance is when the process does not produce a large amount of high pressure export steam due to the lack of demand for export steam. Low or zero export steam production reduces the heat sink for the process, resulting in a large amount of waste heat.
Industry desires to produce purified water in water-stressed regions. The water can be used as make-up water in the catalytic steam-hydrocarbon reforming process, making the process self-sufficient with regard to water. Water can also be sold as a product for industrial and municipal use.
Industry desires to reduce or eliminate water treatment cost in a catalytic steam-hydrocarbon reforming plant. Currently, make-up water needs to be treated in a catalytic steam-hydrocarbon reforming plant so that it meets the requirements for the boiler feed water. These treatments include filtration to remove particulates, demineralization to remove minerals, and deaeration to remove soluble gases such as O2 and CO2.
Industry desires to reduce the capital and energy cost of the catalytic steam-hydrocarbon reforming process. The thermal efficiency of catalytic steam-hydrocarbon reforming processes depends on the utilization of low level heat. When the energy cost is high, more low level heat is recovered for better thermal efficiency or lower energy cost. However, recovering more heat means using more and/or larger heat exchangers, resulting in higher capital cost. In contrast, when the energy cost is low, the capital cost for heat exchangers is minimized with the sacrifice of thermal efficiency or energy cost.